The invention relates to a tab or closure system adhered to an outer film or non-woven wrapper in a disposable absorbent article. The tab or closure is adhered to the film wrapper or outer non-woven cover of the article with an attachment adhesive. In particular, the invention relates to a unique attachment adhesive having enhanced properties for attaching the tab to the film or non-woven. The tab closure system comprises a flexible film having, on one end, means to substantially permanently attach the tab to the disposable article and, on the opposite end, a positioning means such as a mechanical attachment system or a layer of adhesive that can hold the tab to the polymer film outer wrapper or outer non-woven layer during application, positioning, closure or repositioning.
Disposable absorbent articles typically include disposable diapers, adult incontinent pads and other systems for retaining or absorbing substantial quantities of bodily fluids. Such articles are typically used by placing or positioning the disposable article on a human subject and then closing and positioning the article on the subject with closure tabs securing the article to the subject. The tabs are attached to the article during manufacture with an attachment adhesive. The closure tabs also have a mechanical fastening system or a layer of a pressure sensitive adhesive (PSA) that positions or holds the tab to the outer polymer film layer or outer non-woven layer, and act to position or reposition the disposable article. Tabs are generally placed at corner positions of one end of the article and are adhered to opposite ends of the article. Typical fastening tabs have one end which is substantially permanently attached and bonded to the absorbent article and a second free end, which can be attached to the opposite end and used to position or reposition, or maintain the article in place on the user. Typically, the tab is initially attached or bonded to the polymer layer or non-woven with a substantially permanent adhesive during manufacture. In the instance that the positioning adhesive comprises a hot-melt pressure sensitive system, the adhesive used to close or position the article can be the same adhesive than is used to attach the tabs to the corner of the disposable article. When different formulations are used for attachment and positioning, the tab attachment adhesives are typically formulated to permanently attach the tabs to the polyolefin film while the positioning or closure adhesives can be less aggressive and can sometimes be a repositionable hot-melt pressure sensitive adhesive (HMPSA).
One example of a typical tab attachment adhesive is shown in Bany et al., U.S. Pat. No. 5,019,071. That adhesive comprises a styrene/isoprene AB or ABA block copolymer, a solid C5 tackifying resin combined with a diluent aromatic containing aliphatic plasticizing oil. The adhesive disclosed by Bany et al. includes about 33-50 wt % of block copolymer, a plasticizing oil comprising 5 to 45% aromatic, the balance being aliphatic, and a solid essentially aliphatic tackifying resin. This adhesive and the adhesive HL-1696 sold by HB Fuller Company, comprising an SIS triblock polymer, a Benzoflex plasticizer and a tackifier, are characteristic of the tab attachment adhesives currently on the market in this general market.
The tab attachment adhesive of the invention is a substantially permanent adhesive, is typically non-pressure sensitive and has a substantial static shear character. These adhesives are a substantially different class of adhesives than the typical pressure sensitive adhesive used in positioning or adhering absorbent articles to undergarments. One example of such a pressure sensitive adhesive is shown in Beal et al., U.S. Pat. No. 5,429,630. The absorbent article has an elongated shape having an absorbent surface tabs 26 and 28. The Beal et al. article is shown in FIGS. 1 and 2. The absorbent article and the tabs have a pressure sensitive adhesive used to adhere the article to the undergarment. Such a structure does not contain a tab that is attached to an absorbent article using a non-pressure sensitive, substantially permanent adhesive having high shear. In Beal et al., the tabs are adhered not to the absorbent article, but to the undergarment for positioning purposes using a different class of adhesive.
In the past, the attachment adhesives have been difficult to use. In large part, the adhesives used to attach the tabs to the polymer (e.g.) polyolefin film tend to have a relatively short open time, i.e., the time during which the adhesive can form substantially permanent bonds to the polymer film. Such short open times limited manufacturing flexibility. Once the adhesive bonds were formed, the bonds often failed to have either sufficient tensile strength or failed to maintain such bonds at temperatures (i.e. body temperatures) in shear conditions in excess of 100° F. Adhesives that do not meet these criteria often fail to attach the tabs permanently to the polymer film for successful manufacturing purposes.
Substantial need exists for an attachment adhesive for use with a tab and a polymer film having a substantial open time, tensile strength and the ability to survive with a permanent attachment for a substantial period of time at or above 100° F.